1. Field of the Invention
This invention relates to the field of semiconductor processing and manufacturing wherein chemical vapor deposition is used to deposit various films and fill interconnect structures on a semiconductor wafer.
2. Description of Related Art
Chemical vapor deposition (CVD) processes are used to deposit circuit elements on a substrate such as a semiconductor wafer by chemical reduction of vapor of a volatile chemical in contact with the wafer. One such process involves the formation of a tungsten metal layer by reduction of WF6.
Chemical vapor deposition (CVD) systems commonly consist of many valves, tubes, fittings, etc. which are used to control a complex chemical reaction. Any one or more of these systems may fail or deviate by any number of possible mechanisms resulting in air leaks, incorrect reactant flows, and the like and most of these failures have a significant negative impact on the entire CVD process. When these CVD systems are in a manufacturing environment, it is very important that they be monitored so as to not interrupt the normal manufacturing flow except at times of real impact to the quality of the product.
The problem of monitoring CVD reactions has been recognized by those skilled in the art and the prior art discloses many different ways of monitoring the chemical reactions which take place in a CVD reaction chamber. Primarily these methods are directed to monitoring the CVD process for the presence of contaminants such as atmospheric gases or the concentrations of reaction precursors. However, attempts to detect the presence of atmospheric contaminants often fail because of the complexity of the reaction environment in the CVD chamber. If the CVD system were a simple vacuum system like a sputter deposition system, then discerning an air leak would be fairly straightforward because the mass spectrum of the environment inside the chamber would display the characteristic mass spectrum of the air. This is not possible in the CVD process since the characteristic mass spectrum of the air leak is obscured by the mass spectrum of the entire process, product, and carrier gases which are present in significantly higher relative concentrations. Thus, it is desirable to find a more robust method of monitoring CVD processes.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a robust method of monitoring CVD processes.
It is another object of the present invention to provide a method of monitoring CVD processes which overcomes the complexity of the particular CVD reaction or minute variations in the reactant concentrations.
Another object of the present invention is to provide an improved CVD apparatus.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.